My 1954 261 uses the rope seal not a neoprene seal.
Get on Ebay and type in "Victor JV650" they're the original type of rope seal with asbestos fibers.
I believe they come in a blue and white box, I had no luck with today's type of rope seals.

Tim

1951 3100 Chevrolet
1951 Chevrolet Suburban Carryall
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